PHP Arrays

PHP Arrays: Indexed, Associative, & Multidimensional

An array in PHP is an ordered map that associates values to keys. Unlike arrays in C or Java, PHP arrays can hold different data types simultaneously and act as lists, hash tables, dictionaries, queues, and stacks.

Types of PHP Arrays

1. Indexed Arrays: Numeric integer indices starting at index 0.
2. Associative Arrays: Named string keys associated with values.
3. Multidimensional Arrays: Arrays containing nested arrays.

flowchart TD
    A["PHP Array Types"] --> B["Indexed Array"]
    A --> C["Associative Array"]
    A --> D["Multidimensional Array"]
    B --> B1["['Apple', 'Banana', 'Cherry']"]
    C --> C1="['name' => 'Alice', 'role' => 'Admin']"
    D --> D1="[['id' => 1, 'title' => 'A'], ['id' => 2, 'title' => 'B']]"

Essential Array Operations

• count($arr): Returns total element count.
• array_push($arr, $val) or $arr[] = $val: Appends element to end.
• array_merge($arr1, $arr2) or [...$arr1, ...$arr2]: Combines arrays.
• array_filter($arr, callback): Filters elements based on truthy condition.
• array_map(callback, $arr): Transforms each element in array.

Practical Code Example

<?php
declare(strict_types=1);

// 1. Multidimensional Associative Array
$products = [
    ['id' => 101, 'name' => 'Mechanical Keyboard', 'price' => 120.00, 'category' => 'Hardware'],
    ['id' => 102, 'name' => 'Ergonomic Mouse', 'price' => 45.50, 'category' => 'Hardware'],
    ['id' => 103, 'name' => 'Developer PDF Ebook', 'price' => 15.00, 'category' => 'Digital'],
];

// 2. Filter Products (Price > $20) using array_filter
$premiumProducts = array_filter($products, fn(array $item): bool => $item['price'] > 20.0);

// 3. Extract Array Column (Product Names)
$productNames = array_column($premiumProducts, 'name');

// 4. Spread Operator Array Merging (...)
$additionalItems = ['Monitor Stand', 'USB-C Hub'];
$fullInventory = [...$productNames, ...$additionalItems];

echo "Premium Products Count: " . count($premiumProducts) . "
";
echo "Full Inventory List: " . implode(" | ", $fullInventory) . "
";

Best Practices

• Use Short Array Syntax []: Prefer [$a, $b] over legacy array($a, $b).
• Use array_column() for Nested Collection Operations: Easily extract specific fields from tabular array records.
• Use Array Spread Operator [...] for Merging: Faster and cleaner than array_merge().

Self-Check Challenge

Given $users = [['name' => 'John', 'age' => 20], ['name' => 'Jane', 'age' => 30]], write code using array_column() to extract an array of names!